[LLVMdev] [RFC] New ToolsSupport library for stuff that only tools need

Chris Bieneman beanz at apple.com
Mon Oct 20 13:02:59 PDT 2014

There is no real technical requirement for this. Currently we work around the signal handlers by building with ENABLE_CRASH_OVERRIDES=NO, and carrying along the command line parsing code and ToolOutputFile isn’t really a big drain.

This seemed to me like the cleanest way to accomplish a goal of mine. The goal I have is to be able to build an LLVM dylib and llc/opt/etc from the same CMake invocation where the dylib does not have crash overrides and signal handler hooks, but the tools do.

There are other ways to accomplish this, but I felt that separating libLLVMSupport into two libraries seemed the cleanest. An alternate approach that could work for me would be to have the implementation of the hooks only be compiled into the tools.


> On Oct 20, 2014, at 12:57 PM, Chandler Carruth <chandlerc at google.com> wrote:
> The question I have is -- does the actual source code need to move? I'm wondering what aspects require a new library as opposed to different sequence of things happening when initializing LLVM as a library vs. as a tool.
> (We've definitely had trouble with the signal handlers ourselves, but I thought we had solved it by using different code paths to set everything else up...)
> On Mon, Oct 20, 2014 at 12:46 PM, Chris Bieneman <beanz at apple.com <mailto:beanz at apple.com>> wrote:
> There are some pieces of functionality in LLVM today, that make sense for tools like llc, opt, clang, but they aren't relevant for embedded uses like LLVM in the JavaScript JIT. One example of this type of functionality is the signal handlers.
> I'd like to propose migrating content that is specifically designed for tools into a new ToolsSupport library. My initial candidates for the new library would be; anything guarded by ENABLE_CRASH_OVERRIDES, and any functionality specific to tools (i.e. ToolOutputFile and eventually command line parsing— once it can be factored out).
> The primary goal of this is to make it easy for uses of LLVM that aren't command line tools to not include functionality that isn't required for that use case.
> Thoughts?
> -Chris
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